Stem cells are present at all stages of life from embryonic development through adulthood. These cells are still undifferentiated and have the ability to develop into the various, specialized cell types of different tissues. Every day, when thousands of cells in the body die in a natural way, most of the dying cells are replaced by terminally differentiated tissue cells. However, these tissue cells cannot always proliferate enough to replace dead cells. Therefore, adult stem cells provide a supply of progenitor cells that repair and regenerate tissues and organs throughout life. Unfortunately, the regenerative stem cell population in a tissue or organ is depleted over time. This loss of regenerative capacity causes a deterioration in function of that organ and is the reason why people age.
Tissue Resident and Regenerative Cells
Regeneration happens through tissue resident progenitor cells developing into terminally differentiated cells with a specific function. These cells can only differentiate into the cells in that tissue and no other cell lines. Progenitor cells do not live forever and need to be replaced eventually. In every tissue progenitor cells develop from small early stem cells that are distributed throughout the body’s blood vessels, the vasculature. Stromal Vascular Fraction (SVF) recovered from lipoaspirate has been shown to contain a significant amount of different regenerative
cell types, including immune cells, stem cells, and progenitor cells in different stages of their development. The cells in this heterogeneous mixture exert their effects through different modes of action and serve diverse purposes in the process of regeneration of various tissues. Cell culture of SVF depletes many beneficial cells that do not adhere to the plastic culture dish. This makes the freshly prepared SVF the best choice to access the body’s own regenerative resources.
Sources of Stem Cells
Stem cells provide a renewable supply of progenitor cells that can be mobilized and activated to induce tissue healing after injury. They are present at all stages of life from the earliest stages of the embryo throughout the entire adult life. Although, embryonic stem cells, derived from early embryonal stages, exhibit remarkable developmental plasticity, several major issues including ethical concerns, and potential immuno-rejection and tumor formation limit the research and development of
therapies based on these specific stem cells. Primarily due to these issues, research focus has now largely shifted to non-embryonic stem cells, which are derived from perinatal (mainly obtained from the umbilical cord) and “adult” tissues (mainly recovered from the fat tissue and bone marrow). Unlike embryonic stem cells, perinatal and adult stem cells, when used autologously (in the same donor patient), do not raise any ethical, immunological, or oncological concerns.
Mesenchymal Stem Cells
The most common type of adult stem cells used for therapy are referred to as mesenchymal stem cells or mesenchymal stromal cells (MSCs) and are mostly found next to small blood vessels in tissues throughout the body. They are capable of differentiating into multiple cell types such as osteoblasts (bone cells), chondroblasts (cartilage cells) and adipocytes (fat cells), and a subset also exhibit endodermal (liver cells, for example) and a neuroectodermal (nerve cells) differentiation potential. In addition to their cellular renewing properties, MSCs also secrete bioactive mediators, which have beneficial effects such as favoring local cell growth as well as anti-inflammatory effects on their local micro-environment to further positively influence the tissue healing process.
Preparations of adipose-derived regenerative cells (ADRC) including mesenchymal stem cells and regulatory T-lymphocytes can modulate inflammatory response. Research has shown that these cells alter the outcome of the immune response by changing the cytokine secretion of dendritic and T-cell subsets. This results in a shift from a pro-inflammatory environment to an anti-inflammatory or tolerant cell environment.13, 14 MSCs are therefore primarily used to enhance the deficient natural healing of lesions that affect bones, tendons and joints. Their positive therapeutic effects have been demonstrated in several studies in humans and animals.
Stem Cell Recovery
Although MSCs are essentially present in the whole body, isolation from many organs such as heart, brain, skeletal muscle, or liver has limited practicality, since it carries an obvious risk of donor site damage. Therefore, for almost a decade bone marrow (BM) has been the primary source of MSCs for adult stem cell-based therapies. However, since only a very small fraction of the cells in fresh BM aspirate are MSCs (approximately one out of 10.000 recovered cells), cell isolation followed by cumbersome culturing in a GMP laboratory is necessary to obtain enough cells for efficient therapy. This cell manipulation can however induce cellular alterations and limit the differentiation capacity (potency) of MSCs.17
Adipose tissue (AT) consists of approximately one-third adipocytes (fat cells) and two-thirds other cell types, including MSCs, regulatory T-cells, endothelial precursor cells and macrophages, together forming the stromal vascular fraction. Several studies have found no significant qualitative differences between cultured adipose-derived MSC and bone marrow-derived MSC.
However, AT yields significantly more MSCs per unit volume than BM and may be utilized as a fresh cell preparation, rich in ADRC, without the need for expansion in laboratories. Harvesting of adipose tissue is less invasive and yields high counts of regenerative cells. Subcutaneous or abdominal fat tissues are both a rich source for ADRC.18, 19, 20 Thus, high amounts of ADRC can be harvested and isolated in a relatively short time and administered back to the patient, if an adequate method like the InGeneron process is used. Furthermore, minimally manipulated cells result in higher clinical safety and efficacy. Systematic studies confirm that adipose-derived and bone marrow-derived stem cells meet the following criteria:
Advantages of Using Adipose Tissue as a Source for MSCs
- Adipose tissue is abundant in most humans
- Adipose tissue shows a comparatively much higher density of MSC than bone marrow
- An adequate number of MSCs can be recovered from adipose tissue without the further need of culturing
- MSCs can be harvested without any major clinical risk from the adipose tissue using a simple lipoaspiration (fat tissue aspiration) procedure, which is less invasive, causes less discomfort and no donor-site damage compared to bone marrow aspiration
Advantages of Adipose-derived Regenerative Cells
- ADRC are responsible for repair, renewal and regeneration of tissues and act through cell renewal and release of trophic mediators
- ADRC communicate with neighboring cells by direct cell contact and have the ability to protect cells at risk of undergoing apoptosis (inhibiting cell death)
- ADRC show multi-lineage differentiation potential following clonal expansion
- ADRC can be rapidly isolated at point-of-care without the need for expensive equipment and complicated processing
- In addition to their regenerative potential, ADRC exert immune-modulatory functions and can act as strong anti-inflammatory agents13, 14